四则运算

源代码：http://www.cnblogs.com/jinggeer/p/6511788.html   来自博客园

更改后：实现括号运算  支持真分数 

#include<stack> 
#include<iostream> 
#include<deque> 
#include<string> 
using namespace std;

 
bool isPra(char c)
{
if (c == '(' || c == ')')
return true;
else
return false;
}

int getPri(char c)
{
switch (c)
{
case '+':
case '-':
return 0; 
break;
case '*':
case '/':
return 1;  
break;
case '(':
case ')':
return -1; 
break;
}
}

 
void check(char c, stack<char>& coll2, deque<char>& coll3)
{
if (coll2.empty())
{
coll2.push(c);
return;
}

if (isPra(c))
{
if (c == '(')
coll2.push(c);
else
{

while (coll2.top() != '(')
{
char ch = coll2.top();
coll3.push_back(ch);
coll2.pop();
}

 
coll2.pop();
}
}
else  
{
 
char sym = coll2.top();

if (getPri(c) <= getPri(sym))
{

coll2.pop();
 
coll3.push_back(sym);
 
check(c, coll2, coll3);
}
else
{
 
coll2.push(c);
}
}
}

void allocate(deque<char>& coll1, stack<char>& coll2, deque<char>& coll3)
{
while (!coll1.empty())
{
char c = coll1.front();
coll1.pop_front();

if (c >= '0'&&c <= '9')
{
coll3.push_back(c);
}
else
{
 
check(c, coll2, coll3);
}

}

 
while (!coll2.empty())
{
char c = coll2.top();
coll3.push_back(c);
coll2.pop();
}
}

void calculate(deque<char>& coll3, stack<int>& coll4)
{
while (!coll3.empty())
{
char c = coll3.front();
coll3.pop_front();

if (c >= '0'&&c <= '9')
{

int op = c - '0';
coll4.push(op);
}
else 
{
int op1 = coll4.top();
coll4.pop();
int op2 = coll4.top();
coll4.pop();
switch (c)
{
case '+':
coll4.push(op2 + op1);
break;
case '-':
coll4.push(op2 - op1);
break;
case '*':
coll4.push(op2*op1);
break;
case '/':
coll4.push(op2 / op1);  
break;
}
}
}
}

int main()
{
deque<char> coll1; 
stack<char> coll2; 
deque<char> coll3; 
stack<int>coll4;  
string str;
cout << "请输入表达式，按enter结束：" << endl;
cin >> str;
for (int i = 0; i != str.size(); ++i)
{

coll1.push_back(str[i]);
}

allocate(coll1, coll2, coll3);

calculate(coll3, coll4);
cout << "计算结果为:" << coll4.top() << endl;
}